Method for producing vinyl ester polymers having specifically settable dispersity and low polydispersity

Abstract

Methods for producing protective-colloid-stabilized aqueous dispersions of vinyl ester, polymers having weight-average particle diameters Dw of 120 nm to 1,500 nm and a polydispersity PD<1.6 include radically initiated emulsion polymerizations of one or more vinyl esters and optionally one or more additional ethylenically unsaturated monomers in aqueous medium in the presence of one or more protective colloids, wherein an aqueous mixture containing 0 to 90 grams of one more protective colloids per liter of water is provided to the receiver (concentration (C)), and starting with or after the start of the metered addition of one or more initiators, one or more protective colloids and the total amount of vinyl esters used are added in a metered manner, the emulsion polymerizations being performed in the absence of vinyl halogenides.

The invention claimed is: 
     
       1. A process for producing protective colloid-stabilized aqueous dispersions of vinyl ester polymers having weight-average particle diameters Dw of 120 nm to 1500 nm and a polydispersity PD of <1.6
 by means of free-radically initiated emulsion polymerizations of one or more vinyl esters and optionally one or more further ethylenically unsaturated monomers in an aqueous medium in the presence of one or more protective colloids, characterized in that an aqueous mixture comprising 0 to 90 grams of one or more protective colloids per liter of water in the initial charge (concentration (C)) is initially charged and, 
 commencing with or after the start of metered addition of one or more initiators, one or more protective colloids and the total amount of vinyl esters used in the process for producing the protective colloid-stabilized aqueous dispersions are metered in, 
 the emulsion polymerizations being performed in the absence of vinyl halides, and 
 no emulsifiers being used during the emulsion polymerizations. 
 
     
     
       2. The process for producing protective colloid-stabilized aqueous dispersions of vinyl ester polymers as claimed in  claim 1 , characterized in that an aqueous mixture comprising 0.1 to 90 grams of one or more protective colloids per liter of water in the initial charge (concentration (C)) is initially charged. 
     
     
       3. The process for producing protective colloid-stabilized aqueous dispersions of vinyl ester polymers as claimed in  claim 1 , characterized in that the following concentrations (C) are used for the production of dispersions having the following weight-average particle sizes Dw:
 (a) for weight-average particle sizes Dw of 120 to 200 nm the concentration (C) is between 55 and 90 grams of protective colloid per liter of water in the initial charge; 
 (b) for weight-average particle sizes Dw of greater than 200 to less than 500 nm the concentration (C) is between 55 and 15 grams of protective colloid per liter of water in the initial charge; and 
 (c) for weight-average particle sizes Dw of 500 nm the concentration (C) is between 15 and 0.0 grams of protective colloid per liter of water in the initial charge. 
 
     
     
       4. The process for producing protective colloid-stabilized aqueous dispersions of vinyl ester polymers as claimed in  claim 1 , characterized in that the metered addition of one or more protective colloids is effected at an addition rate of 0.1 to 5 grams of protective colloid per liter of water in the initial charge and minute (initial addition rate (VZ)). 
     
     
       5. The process for producing protective colloid-stabilized aqueous dispersions of vinyl ester polymers as claimed in  claim 4 , characterized in that the following initial addition rates (VZ) are used for the production of dispersions having the following weight-average particle sizes Dw:
 (α) for weight-average particle sizes Dw of 120 to 200 nm the initial addition rate (VZ) is 0.1 to 2 grams of protective colloid per liter of water in the initial charge and minute; 
 (β) for weight-average particle sizes Dw of greater than 200 to less than 500 nm the initial addition rate (VZ) is 0.2 to 3 grams of protective colloid per liter of water in the initial charge and minute; and 
 (γ) for weight-average particle sizes Dw of 500 nm the initial addition rate (VZ) is 0.3 to 5 grams of protective colloid per liter of water in the initial charge and minute. 
 
     
     
       6. The process for producing protective colloid-stabilized aqueous dispersions of vinyl ester polymers as claimed in  claim 4 , characterized in that concentrations (C) are between 0.0 and 8 grams of protective colloid per liter of water in the initial charge and the initial addition rate (VZ) is between 0.3 and 3.0 grams of protective colloid per liter of water in the initial charge and minute for the production of dispersions having weight-average particle sizes Dw of 700 nm to 1500 nm. 
     
     
       7. The process for producing protective colloid-stabilized aqueous dispersions of vinyl ester polymers as claimed in  claim 1 , characterized in that the metered addition of one or more protective colloids is commenced when 0.0% to 10% by weight of one or more vinyl esters, based on the total weight of the total amount of vinyl esters used, has been metered in.